<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>02_原生事件绑定</title>
</head>
<body>
<button id="btn1">按钮1</button>
<button id="btn2">按钮2</button>
<button onclick="demo()">按钮3</button>
<script type="text/javascript">
    const btn1 = document.getElementById('btn1');
    btn1.addEventListener('click', () => {
        alert('按钮1');
    });

    const btn2 = document.getElementById('btn2');
    btn2.onclick = () => {
        alert('按钮2');
    };

    function demo() {
        alert('按钮3')
    }
</script>
</body>
</html>